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PHOENIX -- In just a few hours, the three Republicans vying for the GOP nomination for a seat in the U.S. Senate will face off live on 3TV and azfamily.com.

Sen. John McCain is looking for re-election to a fifth term the Senate, but former U.S. Congressman J.D. Hayworth and conservative hopeful Jim Deakin are hoping to knock him out of the running.

Earlier this week, a new poll was released showing that McCain has a substantial lead over Hayworth -- 64 percent to 19 percent. Deakin, who is new to the political stage, had 5 percent. The telephone poll was conducted by the Behavior Research Center between June 30 and July 11 and has a margin of error of plus or minus 6.5 percentage points.

Hayworth's camp has questioned the credibility of the Behavior Research Center and its poll.

Even as final preparations for the debate are under way, an anti-illegal-immigration group is asking Deakin to pull out of the race. The group, Americans for Legal Immigration Political Action Committee, says Deakin could serve as a spoiler. They're worried the Navy veteran will split the "anti-McCain" vote with Hayworth, whom ALI-PAC has endorsed.

Deakin said he won't drop out because he's the best candidate to beat McCain.

Tonight's debate will be aired live and commercial-free starting at 7 p.m. on both 3TV and azfamily.com.